The US subsidiary of leading Japanese automaker Toyota has been subpoenaed by a grand jury in New York, for documents related to defective steering rods in some of its vehicles.

The company has expressed its willingness to cooperate with the inquiry, but it has not revealed details of the subpoena issued late June.

Reports say it is not clear whether the jury inquiry pertains to a 2005 Toyota recall due to a steering relay-rod problem, over which the US National Highway Traffic Safety Administration (NHTSA) began an inquiry this year to verify if the company notified the agency of the defect in due time.

The US recall of about 977,000 Toyota vehicles came after the automaker had initially claimed that the problem was restricted to the Japanese market.

In February, Toyota was subpoenaed by a Manhattan jury for documents on the issue of unintended acceleration of its vehicles and braking problems with its Prius hybrid model.

The company is fighting to save its reputation following the recall of more than 8.5 million vehicles worldwide since October last year, including 6 million in the US.